Look for SCUBA water temps of 79 plus/minus a degree; topside daytime highs mid to upper 70s; night time lows lower 60s; and good to excellent visability.
A drawback of Feb is it's square in El Norte season. These are fronts that result from cold air passing down from North America. They're usually out of the NNE, but can be directly out of the N. They typically involve wind and rain, and the real diving damper is when surface conditions get so rough that the port is closed.
There are about 70 dive ops on Coz. Recommendations of course depend upon what style of diving you dersire and are comfortable with.